Chapter 4 Cartilage and Bone Li Shu-Lei instructor Dept. Histology and Embryology, School of Basic Medical Sciences , Jilin University I Cartilage a specialized connective tissue Characterizers: Cartilage cells (chondrocytes) ground substance is semi-rigid. chondromucoprotein no blood vessels, lymphatic vessels or nerves Types: hyaline cartilage, elastic cartilage, fibrocartilage Hyaline cartilage Distribution Bluish-white Articular surface, rib cartilage, trachea & bronchus Components Chondrocytes Extracellular matrix Perichondrium peripheral cells: immature, small,single , elliptic, flattened perichondrium periphery of hyaline cartilage Deeper part of hyaline cartilage central cell: mature, large, round ，isogenous groups a large centrally-placed nucleus，basophilic cytoplasm Chondrocytes Deeper part of hyaline cartilage isogenous groups Chondrocytes are enclosed by cartilage matrix. lacunae : small cavities occuped by cells Capsule: cartilage matrix surrounding chondrocyte, intense basophilia lacunae cartilage Capsule matrix EM: rough endoplasmic reticulum mitochondria Free ribosomes Golgi complex ----Function: The chondrocytes are involved in the production of fibers and ground substance. collagenous fibrils : not be seen under the light microscope ground substance basophilic main component :chondromucoprotein. Function: retain a large amount of water; nourish chondrocytes cartilage matrix perichondrium : connective tissue The outer zone : more fibers and fibroblast, protection The inner zone : well vascularised , more chondroblasts outer zone cartilage inner zone tissue external ear, eustachian tube, epiglottis , laryngeal cartilages elastic fiber more elasticity and flexibility Chondrocytes capsule Wirelike elastic fiber perichondrium intervertebral discs, the symphysis pubis small amounts of ground substance large number of collagenous fibers Chondrocytes are arranged in rows. 1.4 Histogenesis and Growth of Cartilage Mesenchyme mesenchymal cells chondroblasts chondrocytes 1.4.1 Interstitial growth inner chondrocyte proliferation→ produce fiber and matrix. immature cartilage 1.4.2 Appositional growth Between perichondrium and cartilage Chondroblasts →cartilage cell (chondrocyte) → produce fiber and matrix. growing and mature cartilage II Bone or Osseous Tissue a kind of connective tissue specialized for support and protection bone tissue cells: 4 types matrix: fibers , ground substance Long bone Spongy bone Compact bone Circumferential lamellae Osteon Interstitial lamellae periosteum, endosteum bone marrow four types of cells Osteoprogenitor cell Osteoblast Osteoblast Osteoprogenitor cell Osteocyte Osteocyte Osteoclast bone matrix bone matrix Osteoclast Ideograph of bone tissue lie in endosteum and in the inner zone of the periosteum. small and spindle-shaped an oval nucleus weak basophilic cytoplasm Osteoprogenitor ---Function: cell differentiated into osteoblast an epithelioid layer locate on the surface of new bone tissue cuboidal or low columnar cell Osteoblast strong basophilic cytoplasm Osteoblast New bone tissue Osteoblast EM: short, slender processes rough endoplasmic reticulum Golgi apparatus. ---Function: synthesize bone collagen fiber osteoid promote calcification become osteocytes osteoid small membrane-limited vesicles containing Bone salt calbindin and fine bone mineral cystals ovoid in shape with fine processes Gap junction acidophilic and the dark nucleus located in bone lacuna and bone canaliculus exchange of metabolites bone lacuna bone canaliculus bone lacuna bone canaliculus bone lacuna bone canaliculus reduced organelles connected via gap junctions in bone canaliculus Function: Maintain bone matrix, balance Ca and P Gap junction canaliculus lacuna process multinucleated giant acidophilic cytoplasm located on the surface of the matrix osteoclast Osteoblast Osteocyte matrix lysosomes Mitochondria Rough endoplasmic reticulum Golgi complex ruffled border ---Function: dissolve and absorb bone matrix ---organic matter: collagen fibers , ground substance In one lamella, the fibers are parallel the fibers of adjacent lamellae run at right angles collagen fibers Lamellae ---inorganic matter: bone salts hydroxyapatite crystal: Ca10(PO4)6(OH)2 Needles-shaped lie alongside the collagenous fibrils 2.2.1 Spongy bone with numerous interconnecting cavities 2.2.2 Compact bone the dense areas without cavities three patterns: circumferential lamellae osteons interstitial lamellae outer circumferential lamellae outer circumferential thick and regular lamellae inner circumferential lamellae thin and irregular inner circumferential lamellae between circumferential lamellae long cylinder Haversian lamellae Haversian canal Volkmann’s canal cementing line Volkmann’s canal Haversian lamellae Haversian canal among Haversian systems triangular or irregular shape Interstitial lamellae Haversian systems ---Periosteum: outer layer: Sharpey’s fiber inner layer: blood vessel, nerve, osteoprogenitor cells ---Endosteum: osteoprogenitor cell ---Function:protection, growth, repair,reconstruction outer circumferential lamellae periosteum endosteum Sharpey’s fiber III Histogensis of Bone (Osteogenesis or Ossification) osteoprogenitor cell→ osteoblast → osteoid ↓↓calcification osteocyte + bone matrix ↓ bone tissue osteoclast dissolve reconstruction Intramembranous ossification directly within a membrane of primary connective tissue. Intracartilaginous ossification within a pre-existing cartilaginous model. Mesenchymal cells round up form a blastema osteoblasts differentiate produce primary bone tissue. Osteoblasts are synthesizing collagen form a strand of matrix that traps cells osteoblasts differentiate to become osteocytes Formation of cartilage model Perichondral Ossification (Formation of bone collar) Formation of primary ossification center and bone marrow cavity Formation of secondary ossification center and epiphyses growth of bone by growth of epiphyseal plate (5 zones ) Disappearance of epiphyseal cartilage in adult bone Calcified cartilage zone Ossification zone Cartilage matrix (purple) recently formed bone tissue (red) Bone marrow and fat cells Summary Master the types of cartilage Master the structure of hylaline cartilage Master the types and structure of bone cells (osteoblast & osteoclast) Master the osteon Know the 5 zones of of epiphyseal plate .